Inorganic fiber with improved shrinkage and strength

ABSTRACT

An inorganic fiber containing silica and magnesia as the major fiber components which further includes an intended strontium oxide additive to improve the thermal stability of the fiber. The inorganic fiber exhibits good thermal performance at 1260° C. and greater for 24 hours or more, retains mechanical integrity after exposure to the use temperature, and exhibits low biopersistence in physiological fluids. Also provided are thermal insulation product forms, methods of preparing the inorganic fiber and of thermally insulating articles using thermal insulation prepared from a plurality of the inorganic fibers.

The present application is a continuation of co-pending U.S. Ser. No.14/580,268, filed on Dec. 23, 2014, which claims the benefit of thefiling date under 35 U.S.C. § 119(e) of U.S. Provisional Application Forpatent Ser. No. 62/025,538 filed on Jul. 17, 2014, from whichapplications priority is claimed, and which are incorporated herein byreference.

TECHNICAL FIELD

A high temperature resistant inorganic fiber that is useful as athermal, electrical, or acoustical insulating material, and which has ause temperature of 1260° C. and greater is provided. The hightemperature resistant inorganic fiber is easily manufacturable, exhibitslow shrinkage after exposure to the use temperature, retains goodmechanical strength after exposure to the use temperature, and exhibitslow biopersistence in physiological fluids.

BACKGROUND

The insulation material industry has determined that it is desirable toutilize fibers in thermal, electrical and acoustical insulatingapplications, which are not durable in physiological fluids, that is,fiber compositions which exhibit a low biopersistence in physiologicalfluids.

While candidate materials have been proposed, the use temperature limitof these materials have not been high enough to accommodate many of theapplications to which high temperature resistant fibers are applied. Forexample, such low biopersistence fibers exhibit high shrinkage atservice temperatures and/or reduced mechanical strength when exposed toservice temperatures ranging from 1000° C. to 1400° C. as compared tothe performance of refractory ceramic fibers.

The high temperature resistant, low biopersistence fibers should exhibitminimal shrinkage at expected exposure temperatures, and after prolongedor continuous exposure to the expected use temperatures, in order toprovide effective thermal protection to the article being insulated.

In addition to temperature resistance as expressed by shrinkagecharacteristics that are important in fibers that are used ininsulation, it is also required that the low biopersistence fibers havemechanical strength characteristics during and following exposure to theexpected use or service temperature, that will permit the fiber tomaintain its structural integrity and insulating characteristics in use.

One characteristic of the mechanical integrity of a fiber is its afterservice friability. The more friable a fiber, that is, the more easilyit is crushed or crumbled to a powder, the less mechanical integrity itpossesses. In general, inorganic fibers that exhibit both hightemperature resistance and low biopersistence in physiological fluidsalso exhibit a high degree of after service friability. This results ina brittle fiber lacking the strength or mechanical integrity afterexposure to the service temperature to be able to provide the necessarystructure to accomplish its insulating purpose. Other measures ofmechanical integrity of fibers include compression strength andcompression recovery.

Thus, it is desirable to produce an improved inorganic fiber compositionthat is readily manufacturable from a fiberizable melt of desiredingredients, which exhibits low biopersistence, low shrinkage during andafter exposure to service temperatures of 1260° C. or greater and, whichexhibits low brittleness after exposure to the expected usetemperatures, and which maintains mechanical integrity after exposure touse temperatures of 1260° C. or greater.

Provided is a high temperature resistant alkaline-earth silicate fiberexhibiting improved thermal stability when the inorganic fiber isexposed to elevated temperatures of 1000° C. to 1500° C. It has beenfound that the addition of suitable amounts of strontium to analkaline-earth silicate inorganic fiber reduces fiber shrinkage andenhances mechanical strength beyond that of examples without strontiumoxide additions. Thus, the fiber exhibits low biopersistence inphysiological solutions, reduced linear shrinkage, and improvedmechanical strength after exposure to expected use temperatures.

According to certain illustrative embodiments, the inorganic fibercomprises the fiberization product of about 65 to about 86 weightpercent silica, about 14 to about 35 weight percent magnesia, andstrontium oxide.

According to certain illustrative embodiments, the inorganic fibercomprises the fiberization product of about 65 to about 86 weightpercent silica, about 14 to about 35 weight percent magnesia, andgreater than 0 to about 5 weight percent strontium oxide.

According to certain illustrative embodiments, the inorganic fibercomprises the fiberization product of about 65 to about 86 weightpercent silica, about 14 to about 35 weight percent magnesia, andgreater than 0 to about 4 weight percent strontium oxide.

According to certain illustrative embodiments, the inorganic fibercomprises the fiberization product of about 65 to about 86 weightpercent silica, about 14 to about 35 weight percent magnesia, andgreater than 0 to about 3 weight percent strontium oxide.

According to certain illustrative embodiments, the inorganic fibercomprises the fiberization product of about 65 to about 86 weightpercent silica, about 14 to about 35 weight percent magnesia, and about1 to about 2 weight percent strontium oxide.

According to certain illustrative embodiments, the inorganic fibercomprises the fiberization product of about 65 to about 86 weightpercent silica, about 14 to about 35 weight percent magnesia, about 1 toabout 2 weight percent strontium oxide, less than about 0.3 weightpercent calcia, and about 1.5 weight percent or less alumina.

According to certain illustrative embodiments, the inorganic fibercomprises the fiberization product of about 70 to about 80 weightpercent silica, about 15 to about 30 weight percent magnesia, andgreater than 0 to about 5 weight percent strontium oxide.

According to certain illustrative embodiments, the inorganic fibercomprises the fiberization product of about 72 to about 80 weightpercent silica, about 20 to about 28 weight percent magnesia, andgreater than 0 to about 5 weight percent strontium oxide.

According to certain illustrative embodiments, the inorganic fibercomprises the fiberization product of about 72 to about 80 weightpercent silica, about 20 to about 28 weight percent magnesia, andgreater than 0 to about 4 weight percent strontium oxide.

According to certain illustrative embodiments, the inorganic fibercomprises the fiberization product of about 72 to about 86 weightpercent silica, about 14 to about 28 weight percent magnesia, andgreater than 0 to about 3 weight percent strontium oxide.

According to certain illustrative embodiments, the inorganic fibercomprises the fiberization product of about 72 to about 80 weightpercent silica, about 20 to about 28 weight percent magnesia, and about1 to about 2 weight percent strontium oxide.

According to certain illustrative embodiments, the inorganic fibercomprises the fiberization product of about 72 to about 80 weightpercent silica, about 20 to about 28 weight percent magnesia, about 1 toabout 2 weight percent strontium oxide, less than about 0.3 weightpercent calcia, and about 1.5 weight percent or less alumina.

According to certain illustrative embodiments, the inorganic fibercomprises the fiberization product of about 75 to about 80 weightpercent silica, about 20 to about 25 weight percent magnesia, andgreater than 0 to about 5 weight percent strontium oxide.

According to certain illustrative embodiments, the inorganic fibercomprises the fiberization product of about 75 to about 80 weightpercent silica, about 20 to about 25 weight percent magnesia, andgreater than 0 to about 4 weight percent strontium oxide.

According to certain illustrative embodiments, the inorganic fibercomprises the fiberization product of about 75 to about 80 weightpercent silica, about 20 to about 25 weight percent magnesia, andgreater than 0 to about 3 weight percent strontium oxide.

According to certain illustrative embodiments, the inorganic fibercomprises the fiberization product of about 75 to about 80 weightpercent silica, about 20 to about 25 weight percent magnesia, and about1 to about 2 weight percent strontium oxide.

According to certain illustrative embodiments, the inorganic fibercomprises the fiberization product of about 75 to about 80 weightpercent silica, about 20 to about 25 weight percent magnesia, about 1 toabout 2 weight percent strontium oxide, less than about 0.3 weightpercent calcia, and about 1.5 weight percent or less alumina.

According to certain illustrative embodiments, the inorganic fibercomprises the fiberization product of about 65 to about 86 weightpercent silica, about 14 to about 35 weight percent magnesia, strontiumoxide, and a viscosity modifier.

According to certain illustrative embodiments, the inorganic fibercomprises the fiberization product of greater than 70 weight percentsilica, about 14 to about 35 weight percent magnesia, strontium oxide,and a viscosity modifier.

According to certain illustrative embodiments, the inorganic fibercomprises the fiberization product of about 65 to about 86 weightpercent silica, about 14 to about 35 weight percent magnesia, greaterthan 0 to about 5 weight percent strontium oxide, and a viscositymodifier.

According to certain illustrative embodiments, the inorganic fibercomprises the fiberization product of about 65 to about 86 weightpercent silica, about 14 to about 35 weight percent magnesia, greaterthan 0 to about 4 weight percent strontium oxide, and a viscositymodifier.

According to certain illustrative embodiments, the inorganic fibercomprises the fiberization product of about 65 to about 86 weightpercent silica, about 14 to about 35 weight percent magnesia, greaterthan 0 to about 3 weight percent strontium oxide and a viscositymodifier.

According to certain illustrative embodiments, the inorganic fibercomprises the fiberization product of about 65 to about 86 weightpercent silica, about 14 to about 35 weight percent magnesia, about 1 toabout 2 weight percent strontium oxide and a viscosity modifier.

According to certain illustrative embodiments, the inorganic fibercomprises the fiberization product of about 65 to about 86 weightpercent silica, about 14 to about 35 weight percent magnesia, about 1 toabout 2 weight percent strontium oxide less than about 0.3 weightpercent calcia, and about 1.5 weight percent or less of a viscositymodifier.

According to certain illustrative embodiments, the inorganic fibercomprises the fiberization product of about 70 to about 80 weightpercent silica, about 15 to about 30 weight percent magnesia, greaterthan 0 to about 5 weight percent strontium oxide, and a viscositymodifier.

According to certain illustrative embodiments, the inorganic fibercomprises the fiberization product of about 70 to about 80 weightpercent silica, about 15 to about 30 weight percent magnesia, greaterthan 0 to about 4 weight percent strontium oxide, and a viscositymodifier.

According to certain illustrative embodiments, the inorganic fibercomprises the fiberization product of about 70 to about 80 weightpercent silica, about 15 to about 30 weight percent magnesia, greaterthan 0 to about 3 weight percent strontium oxide, and a viscositymodifier.

According to certain illustrative embodiments, the inorganic fibercomprises the fiberization product of about 70 to about 80 weightpercent silica, about 15 to about 30 weight percent magnesia, about 1 toabout 2 weight percent strontium oxide, and a viscosity modifier.

According to certain illustrative embodiments, the inorganic fibercomprises the fiberization product of about 70 to about 80 weightpercent silica, about 15 to about 30 weight percent magnesia, about 1 toabout 2 weight percent strontium oxide, less than about 0.3 weightpercent calcia and about 1.5 weight percent of less of a viscositymodifier.

According to certain illustrative embodiments, the inorganic fibercomprises the fiberization product of about 72 to about 80 weightpercent silica, about 20 to about 28 weight percent magnesia, greaterthan 0 to about 5 weight percent strontium oxide, and a viscositymodifier.

According to certain illustrative embodiments, the inorganic fibercomprises the fiberization product of about 72 to about 80 weightpercent silica, about 20 to about 28 weight percent magnesia, greaterthan 0 to about 4 weight percent strontium oxide, and a viscositymodifier.

According to certain illustrative embodiments, the inorganic fibercomprises the fiberization product of about 72 to about 80 weightpercent silica, about 20 to about 28 weight percent magnesia, greaterthan 0 to about 3 weight percent strontium oxide, and a viscositymodifier.

According to certain illustrative embodiments, the inorganic fibercomprises the fiberization product of about 72 to about 80 weightpercent silica, about 20 to about 28 weight percent magnesia, about 1 toabout 2 weight percent strontium oxide, and a viscosity modifier.

According to certain illustrative embodiments, the inorganic fibercomprises the fiberization product of about 72 to about 80 weightpercent silica, about 20 to about 28 weight percent magnesia, about 1 toabout 2 weight percent strontium oxide, less than about 0.3 weightpercent calcia, and 1.5 weight percent or less of a viscosity modifier.

According to certain illustrative embodiments, the inorganic fibercomprises the fiberization product of about 72 to about 86 weightpercent silica, about 14 to about 28 weight percent magnesia, greaterthan 0 to about 5 weight percent strontium oxide, and a viscositymodifier.

According to certain illustrative embodiments, the inorganic fibercomprises the fiberization product of about 72 to about 86 weightpercent silica, about 14 to about 28 weight percent magnesia, greaterthan 0 to about 4 weight percent strontium oxide, and a viscositymodifier.

According to certain illustrative embodiments, the inorganic fibercomprises the fiberization product of about 72 to about 86 weightpercent silica, about 14 to about 28 weight percent magnesia, greaterthan 0 to about 3 weight percent strontium oxide, and a viscositymodifier.

According to certain illustrative embodiments, the inorganic fibercomprises the fiberization product of about 72 to about 86 weightpercent silica, about 14 to about 28 weight percent magnesia, about 1 toabout 2 weight percent strontium oxide, and a viscosity modifier.

According to certain illustrative embodiments, the inorganic fibercomprises the fiberization product of about 72 to about 86 weightpercent silica, about 14 to about 28 weight percent magnesia, about 1about 2 weight percent strontium oxide, less than about 0.3 weightpercent calcia, and a 1.5 weight percent or less of a viscositymodifier.

According to certain illustrative embodiments, the inorganic fibercomprises the fiberization product of about 75 to about 80 weightpercent silica, about 20 to about 25 weight percent magnesia, greaterthan 0 to about 5 weight percent strontium oxide, and a viscositymodifier.

According to certain illustrative embodiments, the inorganic fibercomprises the fiberization product of about 75 to about 80 weightpercent silica, about 20 to about 25 weight percent magnesia, greaterthan 0 to about 4 weight percent strontium oxide, and a viscositymodifier.

According to certain illustrative embodiments, the inorganic fibercomprises the fiberization product of about 75 to about 80 weightpercent silica, about 20 to about 25 weight percent magnesia, greaterthan 0 to about 3 weight percent strontium oxide, and a viscositymodifier.

According to certain illustrative embodiments, the inorganic fibercomprises the fiberization product of about 75 to about 80 weightpercent silica, about 20 to about 25 weight percent magnesia, about 1 toabout 2 weight percent strontium oxide, and a viscosity modifier.

According to certain illustrative embodiments, the inorganic fibercomprises the fiberization product of about 75 to about 80 weightpercent silica, about 20 to about 25 weight percent magnesia, about 1 toabout 2 weight percent strontium oxide, less than 0.3 weight percentcalcia, and 1.5 weight percent or less of a viscosity modifier.

Without limitation, and only by way of illustration, suitable viscositymodifiers that may be included in the inorganic fiber compositioninclude alumina, boria, and mixtures of alumina and boria.

According to certain illustrative embodiments, the inorganic fibercomprises the fiberization product of about 65 to about 86 weightpercent silica, about 14 to about 35 weight percent magnesia, strontiumoxide, and alumina as a viscosity modifier.

According to certain illustrative embodiments, the inorganic fibercomprises the fiberization product of about 65 to about 86 weightpercent silica, about 14 to about 35 weight percent magnesia, greaterthan 0 to about 5 weight percent strontium oxide, and alumina as aviscosity modifier.

According to certain illustrative embodiments, the inorganic fibercomprises the fiberization product of about 65 to about 86 weightpercent silica, about 14 to about 35 weight percent magnesia, greaterthan 0 to about 4 weight percent strontium oxide, and alumina as aviscosity modifier.

According to certain illustrative embodiments, the inorganic fibercomprises the fiberization product of about 65 to about 86 weightpercent silica, about 14 to about 35 weight percent magnesia, greaterthan 0 to about 3 weight percent strontium oxide, and alumina as aviscosity modifier.

According to certain illustrative embodiments, the inorganic fibercomprises the fiberization product of about 65 to about 86 weightpercent silica, about 14 to about 35 weight percent magnesia, greaterthan 0 to about 5 weight percent strontium oxide, and greater than 0 toabout 2 weight percent alumina as a viscosity modifier.

According to certain illustrative embodiments, the inorganic fibercomprises the fiberization product of about 65 to about 86 weightpercent silica, about 14 to about 35 weight percent magnesia, greaterthan 0 to about 4 weight percent strontium oxide, and greater than 0 toabout 2 weight percent alumina as a viscosity modifier.

According to certain illustrative embodiments, the inorganic fibercomprises the fiberization product of about 65 to about 86 weightpercent silica, about 14 to about 35 weight percent magnesia, greaterthan 0 to about 3 weight percent strontium oxide, and greater than 0 toabout 2 weight percent alumina as a viscosity modifier.

According to certain illustrative embodiments, the inorganic fibercomprises the fiberization product of about 65 to about 86 weightpercent silica, about 14 to about 35 weight percent magnesia, greaterthan 0 to about 5 weight percent strontium oxide, and boria as aviscosity modifier.

According to certain illustrative embodiments, the inorganic fibercomprises the fiberization product of about 65 to about 86 weightpercent silica, about 14 to about 35 weight percent magnesia, greaterthan 0 to about 4 weight percent strontium oxide, and boria as aviscosity modifier.

According to certain illustrative embodiments, the inorganic fibercomprises the fiberization product of about 65 to about 86 weightpercent silica, about 14 to about 35 weight percent magnesia, greaterthan 0 to about 3 weight percent strontium oxide, and boria as aviscosity modifier.

According to certain illustrative embodiments, the inorganic fibercomprises the fiberization product of about 65 to about 86 weightpercent silica, about 14 to about 35 weight percent magnesia, greaterthan 0 to about 5 weight percent strontium oxide, and a mixture ofalumina and boria as the viscosity modifier.

According to certain illustrative embodiments, the inorganic fibercomprises the fiberization product of about 65 to about 86 weightpercent silica, about 14 to about 35 weight percent magnesia, greaterthan 0 to about 4 weight percent strontium oxide, and a mixture ofalumina and boria as the viscosity modifier.

According to certain illustrative embodiments, the inorganic fibercomprises the fiberization product of about 65 to about 86 weightpercent silica, about 14 to about 35 weight percent magnesia, greaterthan 0 to about 3 weight percent strontium oxide, and a mixture ofalumina and boria as the viscosity modifier.

According to certain illustrative embodiments, the inorganic fibercomprises the fiberization product of about 65 to about 86 weightpercent silica, about 14 to about 35 weight percent magnesia, greaterthan 0 to about 5 weight percent strontium oxide, and a mixture ofgreater than 0 to about 2 weight percent alumina and greater than 0 toabout 1 weight percent boria as the viscosity modifier.

According to certain illustrative embodiments, the inorganic fibercomprises the fiberization product of about 65 to about 86 weightpercent silica, about 14 to about 35 weight percent magnesia, greaterthan 0 to about 4 weight percent strontium oxide, and a mixture ofgreater than 0 to about 2 weight percent alumina and greater than 0 toabout 1 weight percent boria as the viscosity modifier.

According to certain illustrative embodiments, the inorganic fibercomprises the fiberization product of about 65 to about 86 weightpercent silica, about 14 to about 35 weight percent magnesia, greaterthan 0 to about 3 weight percent strontium oxide, and a mixture ofgreater than 0 to about 2 weight percent alumina and greater than 0 toabout 1 weight percent boria as the viscosity modifier.

According to certain illustrative embodiments, the inorganic fibercomprises the fiberization product of about 70 to about 80 weightpercent silica, about 15 to about 30 weight percent magnesia, greaterthan 0 to about 5 weight percent strontium oxide, and from 0 to about 2weight percent alumina as a viscosity modifier.

According to certain illustrative embodiments, the inorganic fibercomprises the fiberization product of about 72 to about 80 weightpercent silica, about 20 to about 28 weight percent magnesia, greaterthan 0 to about 5 weight percent strontium oxide, and from 0 to about 2weight percent alumina as a viscosity modifier.

According to certain illustrative embodiments, the inorganic fibercomprises the fiberization product of about 72 to about 86 weightpercent silica, about 14 to about 28 weight percent magnesia, greaterthan 0 to about 5 weight percent strontium oxide, and from 0 to about 2weight percent alumina as a viscosity modifier.

According to certain illustrative embodiments, the inorganic fibercomprises the fiberization product of about 75 to about 80 weightpercent silica, about 20 to about 25 weight percent magnesia, greaterthan 0 to about 5 weight percent strontium oxide, and from 0 to about 2weight percent alumina as a viscosity modifier.

According to certain illustrative embodiments, the inorganic fibercomprises the fiberization product of about 70 to about 80 weightpercent silica, about 15 to about 25 weight percent magnesia, greaterthan 0 to about 5 weight percent strontium oxide, and from 0 to about 1weight percent boria as a viscosity modifier.

According to certain illustrative embodiments, the inorganic fibercomprises the fiberization product of about 72 to about 80 weightpercent silica, about 20 to about 28 weight percent magnesia, greaterthan 0 to about 5 weight percent strontium oxide, and from 0 to about 1weight percent boria as a viscosity modifier.

According to certain illustrative embodiments, the inorganic fibercomprises the fiberization product of about 72 to about 86 weightpercent silica, about 14 to about 28 weight percent magnesia, greaterthan 0 to about 5 weight percent strontium oxide, and from 0 to about 1weight percent boria as a viscosity modifier.

According to certain illustrative embodiments, the inorganic fibercomprises the fiberization product of about 75 to about 80 weightpercent silica, about 20 to about 25 weight percent magnesia, greaterthan 0 to about 5 weight percent strontium oxide, and from 0 to about 1weight percent boria as a viscosity modifier.

According to certain illustrative embodiments, the inorganic fibercomprises the fiberization product of about 70 to about 80 weightpercent silica, about 15 to about 25 weight percent magnesia, greaterthan 0 to about 5 weight percent strontium oxide, and from 0 to about 3weight percent of a mixture of alumina and boria as a viscositymodifier.

According to certain illustrative embodiments, the inorganic fibercomprises the fiberization product of about 72 to about 80 weightpercent silica, about 20 to about 28 weight percent magnesia, greaterthan 0 to about 5 weight percent strontium oxide, and from 0 to about 3weight percent of a mixture of alumina and boria as a viscositymodifier.

According to certain illustrative embodiments, the inorganic fibercomprises the fiberization product of about 72 to about 86 weightpercent silica, about 14 to about 28 weight percent magnesia, greaterthan 0 to about 5 weight percent strontium oxide, and from 0 to about 3weight percent of a mixture of alumina and boria as a viscositymodifier.

According to certain illustrative embodiments, the inorganic fibercomprises the fiberization product of about 75 to about 80 weightpercent silica, about 20 to about 25 weight percent magnesia, greaterthan 0 to about 5 weight percent strontium oxide, and from 0 to about 3weight percent of a mixture of alumina and boria as a viscositymodifier.

According to certain illustrative embodiments, the inorganic fibercomprises the fiberization product of about 65 to about 86 weightpercent silica, about 14 to about 35 weight percent magnesia, strontiumoxide, and greater than 0 to about 11 weight percent zirconia.

According to certain illustrative embodiments, the inorganic fibercomprises the fiberization product of about 65 to about 86 weightpercent silica, about 14 to about 35 weight percent magnesia, greaterthan 0 to about 5 weight percent strontium oxide, and greater than 0 toabout 11 weight percent zirconia.

According to certain illustrative embodiments, the inorganic fibercomprises the fiberization product of about 65 to about 86 weightpercent silica, about 14 to about 35 weight percent magnesia, greaterthan 0 to about 4 weight percent strontium oxide, and greater than 0 toabout 11 weight percent zirconia.

According to certain illustrative embodiments, the inorganic fibercomprises the fiberization product of about 65 to about 86 weightpercent silica, about 14 to about 35 weight percent magnesia, greaterthan 0 to about 3 weight percent strontium oxide, and greater than 0 toabout 11 weight percent zirconia.

According to certain illustrative embodiments, the inorganic fibercomprises the fiberization product of about 65 to about 86 weightpercent silica, about 14 to about 35 weight percent magnesia, strontiumoxide, greater than 0 to about 11 weight percent zirconia, and aviscosity modifier.

According to certain illustrative embodiments, the inorganic fibercomprises the fiberization product of about 65 to about 86 weightpercent silica, about 14 to about 35 weight percent magnesia, greaterthan 0 to about 5 weight percent strontium oxide, greater than 0 toabout 11 weight percent zirconia, and a viscosity modifier.

According to certain illustrative embodiments, the inorganic fibercomprises the fiberization product of about 65 to about 86 weightpercent silica, about 14 to about 35 weight percent magnesia, greaterthan 0 to about 4 weight percent strontium oxide, greater than 0 toabout 11 weight percent zirconia, and a viscosity modifier.

According to certain illustrative embodiments, the inorganic fibercomprises the fiberization product of about 65 to about 86 weightpercent silica, about 14 to about 35 weight percent magnesia, greaterthan 0 to about 3 weight percent strontium oxide, greater than 0 toabout 11 weight percent zirconia, and a viscosity modifier.

According to certain illustrative embodiments, the inorganic fibercomprises the fiberization product of about 65 to about 86 weightpercent silica, about 14 to about 35 weight percent magnesia, strontiumoxide, greater than 0 to about 11 weight percent zirconia, and aviscosity modifier comprising alumina, boria, or a mixture of aluminaand boria.

According to certain illustrative embodiments, the inorganic fibercomprises the fiberization product of about 65 to about 86 weightpercent silica, about 14 to about 35 weight percent magnesia, greaterthan 0 to about 5 weight percent strontium oxide, greater than 0 toabout 11 weight percent zirconia, and a viscosity modifier comprisingalumina, boria, or a mixture of alumina and boria.

According to certain illustrative embodiments, the inorganic fibercomprises the fiberization product of about 65 to about 86 weightpercent silica, about 14 to about 35 weight percent magnesia, greaterthan 0 to about 4 weight percent strontium oxide, greater than 0 toabout 11 weight percent zirconia, and a viscosity modifier comprisingalumina, boria, or a mixture of alumina and boria.

According to certain illustrative embodiments, the inorganic fibercomprises the fiberization product of about 65 to about 86 weightpercent silica, about 14 to about 35 weight percent magnesia, greaterthan 0 to about 3 weight percent strontium oxide, greater than 0 toabout 11 weight percent zirconia, and a viscosity modifier comprisingalumina, boria, or a mixture of alumina and boria.

According to certain illustrative embodiments, the inorganic fibercontains 1 weight percent or less calcia. According to otherillustrative embodiments, the inorganic fiber contains 0.5 weightpercent or less calcia. According to further illustrative embodiments,the inorganic fiber contains 0.3 weight percent or less calcia.

According to certain embodiments, the inorganic fiber containssubstantially no alkali metal oxide.

According to certain embodiments, provided is a high temperatureresistant inorganic fiber which exhibits a linear shrinkage of about 10%or less when exposed a use temperature of 1260° C. or greater for 24hours or longer, and which maintains mechanical integrity after exposureto the use temperature, and which exhibits low biopersistence inphysiological fluids.

According to certain embodiments, the high temperature resistantinorganic fiber exhibits a linear shrinkage of about 5% or less whenexposed a use temperature of 1260° C. or greater for 24 hours or longer,and which maintains mechanical integrity after exposure to the usetemperature, and which exhibits low biopersistence in physiologicalfluids.

According to certain embodiments, the high temperature resistantinorganic fiber exhibits a linear shrinkage of about 4% or less whenexposed a use temperature of 1260° C. or greater for 24 hours or longer,maintains mechanical integrity after exposure to the use temperature,and which exhibits low biopersistence in physiological fluids.

According to certain embodiments, provided is a high temperatureresistant inorganic fiber which exhibits a linear shrinkage of about 10%or less when exposed a use temperature of 1400° C. or greater for 24hours or longer, and which maintains mechanical integrity after exposureto the use temperature, and which exhibits low biopersistence inphysiological fluids.

According to certain embodiments, the high temperature resistantinorganic fiber exhibits a linear shrinkage of about 5% or less whenexposed a use temperature of 1400° C. or greater for 24 hours or longer,and which maintains mechanical integrity after exposure to the usetemperature, and exhibit low biopersistence in physiological fluids.

According to certain embodiments, the high temperature resistantinorganic fiber exhibits a linear shrinkage of about 4% or less whenexposed a use temperature of 1400° C. or greater for 24 hours or longer,maintains mechanical integrity after exposure to the use temperature,and which exhibits low biopersistence in physiological fluids.

According to certain illustrative embodiments, provided is a method forpreparing a high temperature resistant inorganic fiber having a usetemperature of 1260° C. or greater, which maintains mechanical integrityafter exposure to the use temperature, and which exhibits lowbiopersistence in physiological fluids. The method for preparing thefiber comprises forming a melt with ingredients comprising about 65 toabout 86 weight percent silica, about 14 to about 35 weight percentmagnesia and strontium oxide, and producing fibers from the melt.

According to certain illustrative embodiments, the method for preparingthe inorganic fiber comprises forming a melt with ingredients comprisingabout 65 to about 86 weight percent silica, about 14 to about 35 weightpercent magnesia, and greater than 0 to about 5 weight percent strontiumoxide, and producing fibers from the melt.

According to certain illustrative embodiments, the method for preparingthe inorganic fiber comprises forming a melt with ingredients comprisingabout 65 to about 86 weight percent silica, about 14 to about 35 weightpercent magnesia, and greater than 0 to about 4 weight percent strontiumoxide, and producing fibers from the melt.

According to certain illustrative embodiments, the method for preparingthe inorganic fiber comprises forming a melt with ingredients comprisingabout 65 to about 86 weight percent silica, about 14 to about 35 weightpercent magnesia, and greater than 0 to about 3 weight percent strontiumoxide, and producing fibers from the melt.

According to certain illustrative embodiments, the method for preparingthe inorganic fiber comprises forming a melt with ingredients comprisingabout 65 to about 86 weight percent silica, about 14 to about 35 weightpercent magnesia, and about 1 to about 2 weight percent strontium oxide,and producing fibers from the melt.

According to certain illustrative embodiments, the method for preparingthe inorganic fiber comprises forming a melt with ingredients comprisingabout 65 to about 86 weight percent silica, about 14 to about 35 weightpercent magnesia, about 1 to about 2 weight percent strontium oxide,about 0.3 weight percent or less calcia, and 1.5 weight percent or lessalumina, and producing fibers from the melt.

According to certain illustrative embodiments, the method for preparingthe inorganic fiber comprises forming a melt with ingredients comprisingabout 65 to about 86 weight percent silica, about 14 to about 35 weightpercent magnesia, strontium oxide, and a viscosity modifier, andproducing fibers from the melt.

According to certain illustrative embodiments, the method for preparingthe inorganic fiber comprises forming a melt with ingredients comprisingabout 65 to about 86 weight percent silica, about 14 to about 35 weightpercent magnesia, greater than 0 to about 5 weight percent strontiumoxide, and a viscosity modifier, and producing fibers from the melt.

According to certain illustrative embodiments, the method for preparingthe inorganic fiber comprises forming a melt with ingredients comprisingabout 65 to about 86 weight percent silica, about 14 to about 35 weightpercent magnesia, greater than 0 to about 4 weight percent strontiumoxide, and a viscosity modifier, and producing fibers from the melt.

According to certain illustrative embodiments, the method for preparingthe inorganic fiber comprises forming a melt with ingredients comprisingabout 65 to about 86 weight percent silica, about 14 to about 35 weightpercent magnesia, greater than 0 to about 3 weight percent strontiumoxide, and a viscosity modifier, and producing fibers from the melt.

According to certain illustrative embodiments, the method for preparingthe inorganic fiber comprises forming a melt with ingredients comprisingabout 65 to about 86 weight percent silica, about 14 to about 35 weightpercent magnesia, about 1 to about 2 weight percent strontium oxide, anda viscosity modifier, and producing fibers from the melt.

According to certain illustrative embodiments, the method for preparingthe inorganic fiber comprises forming a melt with ingredients comprisingabout 65 to about 86 weight percent silica, about 14 to about 35 weightpercent magnesia, about 1 to about 2 weight percent strontium oxide,about 0.3 or less calcia, and 1.5 weight percent or less of a viscositymodifier, and producing fibers from the melt.

According to certain illustrative embodiments, the method for preparingthe inorganic fiber comprises forming a melt with ingredients comprisingabout 65 to about 86 weight percent silica, about 14 to about 35 weightpercent magnesia, strontium oxide, greater than 0 to about 11 weightpercent zirconia, and a viscosity modifier, and producing fibers fromthe melt.

According to certain illustrative embodiments, the method for preparingthe inorganic fiber comprises forming a melt with ingredients comprisingabout 65 to about 86 weight percent silica, about 14 to about 35 weightpercent magnesia, greater than 0 to about 5 weight percent strontiumoxide, greater than 0 to about 11 weight percent zirconia, and aviscosity modifier, and producing fibers from the melt.

According to certain illustrative embodiments, the method for preparingthe inorganic fiber comprises forming a melt with ingredients comprisingabout 65 to about 86 weight percent silica, about 14 to about 35 weightpercent magnesia, greater than 0 to about 4 weight percent strontiumoxide, greater than 0 to about 11 weight percent, and a viscositymodifier, and producing fibers from the melt.

According to certain illustrative embodiments, the method for preparingthe inorganic fiber comprises forming a melt with ingredients comprisingabout 65 to about 86 weight percent silica, about 14 to about 35 weightpercent magnesia, greater than 0 to about 3 weight percent strontiumoxide, greater than 0 to about 11 weight percent zirconia, and aviscosity modifier, and producing fibers from the melt.

According to certain illustrative embodiments, the method for preparingthe inorganic fiber comprises forming a melt with ingredients comprisingabout 65 to about 86 weight percent silica, about 14 to about 35 weightpercent magnesia, about 1 to about 2 weight percent strontium oxide,greater than 0 to about 11 weight percent zirconia, and a viscositymodifier, and producing fibers from the melt.

According to certain illustrative embodiments, the method for preparingthe inorganic fiber comprises forming a melt with ingredients comprisingabout 65 to about 86 weight percent silica, about 14 to about 35 weightpercent magnesia, about 1 to about 2 weight percent strontium oxide,about 0.3 weight percent or less calcia, greater than 0 to about 11weight percent zirconia, and 1.5 weight percent or less of a viscositymodifier, and producing fibers from the melt.

Without limitation, the viscosity modifier that is added to the melt ofingredients to prepare the inorganic fiber may be selected from alumina,boria, and mixtures of alumina and boria. The viscosity modifier isincluded in the melt of ingredients in an amount effective render themelt fiberizable.

Also provided is a method of thermally insulating an article withfibrous insulation prepared from a plurality of the presently disclosedhigh temperature resistant low biopersistent inorganic fibers of any ofthe above disclosed illustrative embodiments. The method includesdisposing on, in, near or around the article to be thermally insulated,a thermal insulation material comprising a plurality of the inorganicfibers.

Also provided is an inorganic fiber containing article, as describedabove, comprising at least one of bulk fiber, blankets, blocks, boards,caulking compositions, cement compositions, coatings, felts, mats,moldable compositions, modules, papers, pumpable compositions, puttycompositions, sheets, tamping mixtures, vacuum cast shapes, vacuum castforms, or woven textiles (for example, braids, cloths, fabrics, ropes,tapes, sleeving, wicking).

In order for a glass composition to be a viable candidate for producinga satisfactory high temperature resistant fiber product, the fiber to beproduced must be manufacturable, sufficiently soluble (ie, having lowbiopersistence) in physiological fluids, and capable of surviving hightemperatures with minimal shrinkage and minimal loss of mechanicalintegrity during exposure to the high service temperatures.

The present inorganic fiber exhibits low biopersistence in physiologicalfluids. By “low biopersistence” in physiological fluids, it is meantthat the inorganic fiber at least partially dissolves in such fluids,such as simulated lung fluid, during in vitro tests.

Biopersistence may be tested by measuring the rate at which mass is lostfrom the fiber (ng/cm²-hr) under conditions which simulate thetemperature and chemical conditions found in the human lung. This testconsists of exposing approximately 0.1 g of de-shotted fiber to 50 ml ofsimulated lung fluid (SLF) for 6 hours. The entire test system ismaintained at 37° C., to simulate the temperature of the human body.

After the SLF has been exposed to the fiber, it is collected andanalyzed for glass constituents using Inductively Coupled PlasmaSpectroscopy. A “blank” SLF sample is also measured and used to correctfor elements present in the SLF. Once this data has been obtained, it ispossible to calculate the rate at which the fiber has lost mass over thetime interval of the study. The fibers are significantly lessbiopersistent than normal refractory ceramic fiber in simulated lungfluid.

“Viscosity” refers to the ability of a glass melt to resist flow orshear stress. The viscosity-temperature relationship is critical indetermining whether it is possible to fiberize a given glasscomposition. An optimum viscosity curve would have a low viscosity (5-50poise) at the fiberization temperature and would gradually increase asthe temperature decreased. If the melt is not sufficiently viscous (i.e.too thin) at the fiberization temperature, the result is a short, thinfiber, with a high proportion of unfiberized material (shot). If themelt is too viscous at the fiberization temperature, the resulting fiberwill be extremely coarse (high diameter) and short.

Viscosity is dependent upon melt chemistry, which is also affected byelements or compounds that act as viscosity modifiers. Viscositymodifiers permit fibers to be blown or spun from the fiber melt. It isdesirable, however, that such viscosity modifiers, either by type oramount, do not adversely impact the solubility, shrink resistance, ormechanical strength of the blown or spun fiber.

One approach to testing whether a fiber of a defined composition can bereadily manufactured at an acceptable quality level is to determinewhether the viscosity curve of the experimental chemistry matches thatof a known product which can be easily fiberized. Viscosity-temperatureprofiles may be measured on a viscometer, capable of operating atelevated temperatures. In addition, an adequate viscosity profile may beinferred by routine experimentation, examining the quality of fiber(index, diameter, length) produced. The shape of the viscosity vs.temperature curve for a glass composition is representative of the easewith which a melt will fiberize and thus, of the quality of theresulting fiber (affecting, for example, the fiber's shot content, fiberdiameter, and fiber length). Glasses generally have low viscosity athigh temperatures. As temperature decreases, the viscosity increases.The value of the viscosity at a given temperature will vary as afunction of the composition, as will the overall steepness of theviscosity vs. temperature curve. The present fiber melt compositionpossesses a viscosity profile of a readily manufacturable fiber.

Linear shrinkage of an inorganic fiber is a good measure of a fiber'sdimensional stability at high temperatures or of its performance at aparticular continuous service or use temperature. Fibers are tested forshrinkage by forming them into a mat and needle punching the mattogether into a blanket of approximately 4-10 pounds per cubic footdensity and a thickness of about 1 inch. Such pads are cut into 3 inch×5inch pieces and platinum pins are inserted into the face of thematerial. The separation distance of these pins is then carefullymeasured and recorded. The pad is then placed into a furnace, ramped totemperature and held at the temperature for a fixed period of time.After heating, the pin separation is again measured to determine thelinear shrinkage that pad has experienced.

In one such test, the length and width of the fiber pieces werecarefully measured, and the pad was placed in a furnace and brought to atemperature of 1260 or 1400° C. for 24. After cooling, the lateraldimensions were measured and the linear shrinkage was determined bycomparing “before” and “after” measurements. If the fiber is availablein blanket form, measurements may be made directly on the blanketwithout the need to form a pad.

Mechanical integrity is also an important property since the fiber mustsupport its own weight in any application and must also be able toresist abrasion due to moving air or gas. Indications of fiber integrityand mechanical strength are provided by visual and tactile observations,as well as mechanical measurement of these properties of after-servicetemperature exposed fibers. The ability of the fiber to maintain itsintegrity after exposure to the use temperature may also be measuredmechanically by testing for compression strength and compressionrecovery. These tests measure, respectively, how easily the pad may bedeformed and the amount of resiliency (or compression recovery) the padexhibits after a compression of 50%. Visual and tactile observationsindicate that the present inorganic fiber remains intact and maintainsits form after exposure to a use temperature of at least 1260 or 1400°C.

According to certain embodiments, the low shrinkage, high temperatureresistant inorganic fiber comprises the fiberization product of a meltcontaining magnesia and silica as the primary constituents. The lowbiopersistent inorganic fibers are made by standard glass and ceramicfiber manufacturing methods. Raw materials, such as silica, any suitablesource of magnesia such as enstatite, forsterite, magnesia, magnesite,calcined magnesite, magnesium zirconate, periclase, steatite, or talc.Strontium may be included in the fiber melt as SrO and/or SrCO₃. Ifzirconia is included in the fiber melt, any suitable source of zirconiasuch as baddeleyite, magnesium zirconate, zircon or zirconia, areintroduced into a suitable furnace where they are melted and blown usinga fiberization nozzle, or spun, either in a batch or a continuous mode.

The inorganic fiber comprising the fiberization product of magnesia andsilica is referred to as a “magnesium-silicate” fiber. The lowshrinkage, high temperature resistant inorganic fiber also comprises astrontium oxide-bearing raw material component as part of the fiber meltchemistry.

According to certain embodiments, the present inorganic fiber has anaverage diameter of greater than 2 microns.

According to certain embodiments, the present inorganic fiber exhibitslow shrinkage and good mechanical strength at temperatures from about1100° C. to about 1500° C., and low biopersistence.

According to certain embodiments, the present inorganic fiber exhibitslow shrinkage and good mechanical strength at temperatures from about1260° C. to about 1500° C., and low biopersistence.

According to certain embodiments, the present inorganic fiber exhibitslow shrinkage and good mechanical strength at temperatures from about1260° C. to about 1400° C., and low biopersistence.

According to certain embodiments, the present inorganic fiber exhibitslow shrinkage and good mechanical strength at temperatures from about1400° C. to about 1500° C., and low biopersistence.

In addition to magnesia, silica and strontium oxide, themagnesium-silicate fiber containing a strontium oxide addition maycontain calcia impurity. In certain embodiments, the fiber does notcontain more than about 1 weight percent calcia impurity. In otherembodiments, the fiber contains less than 0.5 weight percent calciaimpurity. In other embodiments, the fiber contains less than 0.3 weightpercent calcia.

The magnesium-silicate fibers containing an intended strontium oxideaddition exhibit a linear shrinkage after exposure to a servicetemperature of 1400° C. for 24 hours of about 10 percent or less. Inother embodiments, the magnesium-silicate fibers containing an intendedstrontium oxide addition exhibit a linear shrinkage after exposure to aservice temperature of 1400° C. for 24 hours of about 5 percent or less.In other embodiments, the magnesium-silicate fibers containing anintended strontium oxide addition exhibit a linear shrinkage afterexposure to a service temperature of 1400° C. for 24 hours of about 4percent or less.

The magnesium-silicate fibers containing an intended strontium oxideaddition are useful for thermal insulating applications at continuousservice or operating temperatures of at least 1260° C. or greater.According to certain embodiments, the magnesium-silicate fiberscontaining strontium oxide are useful for thermal insulatingapplications at continuous service or operating temperatures of at least1400° C. and it has been found that the magnesium-silicate fiberscontaining the strontium oxide addition do not melt until they areexposed to a temperature of 1500° C. or greater.

The inorganic fibers may be prepared by fiber blowing or fiber spinningtechniques. A suitable fiber blowing technique includes the steps ofmixing the starting raw materials containing magnesia, silica, strontiumoxide, viscosity modifier, and optional zirconia together to form amaterial mixture of ingredients, introducing the material mixture ofingredients into a suitable vessel or container, melting the materialmixture of ingredients for discharge through a suitable nozzle, andblowing a high pressure gas onto the discharged flow of molten materialmixture of ingredients to form the fibers.

A suitable fiber spinning technique includes the steps of mixing thestarting raw materials together to form a material mixture ofingredients, introducing the material mixture of ingredients into asuitable vessel or container, melting the material mixture ofingredients for discharge through a suitable nozzle onto spinningwheels. The molten stream then cascades over the wheels, coating thewheels and being thrown off through centripetal forces, thereby formingfibers.

In some embodiments, the fiber is produced from a melt of raw materialsby subjecting the molten stream to a jet of high pressure/high velocityair or by pouring the melt onto rapidly spinning wheels and spinningfiber centrifugally. The strontium oxide is provided as an additive tothe melt, and a suitable source of the strontium oxide raw material issimply added at the proper amount to the raw materials being melted.

The addition of a strontium oxide as a component of the raw materialswhich are fiberized results in a decrease of linear shrinkage of theresulting fiber after exposure to the use temperature.

In addition to the strontium oxide bearing containing compound, theviscosity of the material melt of ingredients may optionally becontrolled by the presence of viscosity modifiers, in an amountsufficient to provide the fiberization required for the desiredapplications. The viscosity modifiers may be present in the rawmaterials which supply the main components of the melt, or may, at leastin part, be separately added. Desired particle size of the raw materialsis determined by furnacing conditions, including furnace size (SEF),pour rate, melt temperature, residence time, and the like.

The fiber may be manufactured with existing fiberization technology andformed into multiple thermal insulation product forms, including but notlimited to bulk fibers, fiber-containing blankets, boards, papers,felts, mats, blocks, modules, coatings, cements, moldable compositions,pumpable compositions, putties, ropes, braids, wicking, textiles (suchas cloths, tapes, sleeving, string, yarns, etc . . . ), vacuum castshapes and composites. The fiber may be used in combination withconventional materials utilized in the production of fiber-containingblankets, vacuum cast shapes and composites, as a substitute forconventional refractory ceramic fibers. The fiber may be used alone orin combination with other materials, such as binders and the like, inthe production of fiber-containing paper and felt.

The fiber may be easily melted by standard glass furnacing methods,fiberized by standard RCF fiberization equipment, and is soluble insimulated body fluids.

A method of insulating an article using a thermal insulation containingthe disclosed magnesium-silicate fibers is also provided. The method ofinsulating an article includes disposing on, in, near, or around thearticle to be insulated, a thermal insulation material that contains themagnesium-silicate fibers containing an intended strontium oxideaddition.

The high temperature resistant inorganic fibers are readilymanufacturable from a melt having a viscosity suitable for blowing orspinning fiber, are non-durable in physiological fluids, exhibit goodmechanical strength up to the service temperature, exhibit excellentlinear shrinkage up to 1400° C. and above, and improved viscosity forfiberization.

EXAMPLES

The following examples are set forth to describe illustrativeembodiments of the magnesium-silicate fibers containing strontium oxideaddition in further detail and to illustrate the methods of preparingthe inorganic fibers, preparing thermal insulating articles containingthe fibers and using the fibers as thermal insulation. However, theexamples should not be construed as limiting the fiber, the fibercontaining articles, or the processes of making or using the fibers asthermal insulation in any manner.

Linear Shrinkage

A shrinkage pad was prepared by needling a fiber mat using a bank offelting needles. A 3 inch×5 inch test piece was cut from the pad and wasused in the shrinkage testing. The length and width of the test pad wascarefully measured. The test pad was then placed into a furnace andbrought to a temperature of 1400° C. for 24 hours. After heating for 24hours, the test pad was removed from the test furnace and cooled. Aftercooling, the length and width of the test pad were measured again. Thelinear shrinkage of the test pad was determined by comparing the“before” and “after” dimensional measurements.

A second shrinkage pad was prepared in a manner similar to thatdisclosed for the first shrinkage pad. However, the second shrinkage padwas placed in a furnace and brought to a temperature of 1260° C. for 24hours. After heating for 24 hours, the test pad was removed from thetest furnace and cooled. After cooling, the length and width of the testpad were measured again. The linear shrinkage of the test pad wasdetermined by comparing the “before” and “after” dimensionalmeasurements.

Compression Recovery

The ability of the inorganic fibers to retain mechanical strength afterexposure to a use temperature was evaluated by a compression recoverytest. Compression recovery is a measure of the mechanical performance ofan inorganic fiber in response to the exposure of the fiber to a desireduse temperature for a given period of time. Compression recovery ismeasured by firing test pads manufactured from the inorganic fibermaterial to the test temperature for the selected period of time. Thefired test pads are thereafter compressed to half of their originalthickness and allowed to rebound. The amount of rebound is measured aspercent recovery of the compressed thickness of the pad. Compressionrecovery was measured after exposure to use temperatures of 1260° C. for24 hours, and 1400° C. for 24 hours. According to certain illustrativeembodiments, the test pads manufactured from the inorganic fibersexhibit a compression recovery of at least 10 percent.

Fiber Dissolution

The inorganic fiber is non-durable or non-biopersistent in physiologicalfluids. By “non-durable” or “non-biopersistent” in physiological fluidsit is meant that the inorganic fiber at least partially dissolves ordecomposes in such fluids, such as simulated lung fluid, during in vitrotests described herein.

The biopersistence test measures the rate at which mass is lost from thefiber (ng/cm²-hr) under conditions which simulate the temperature andchemical conditions found in the human lung. In particular, the fibersexhibit low biopersistence in Simulated Lung Fluid at a pH of 7.4.

To measure the dissolution rate of fibers in simulated lung fluid,approximately 0.1 g of fiber is placed into a 50 ml centrifuge tubecontaining simulated lung fluid which has been warmed to 37° C. This isthen placed into a shaking incubator for 6 hours and agitated at 100cycles per minute. At the conclusion of the test, the tube iscentrifuged and the solution is poured into a 60 ml syringe. Thesolution is then forced through a 0.45 μm filter to remove anyparticulate and tested for glass constituents using Inductively CoupledPlasma Spectroscopy analysis. This test may be conducted using either anear-neutral pH solution or an acidic solution. Although no specificdissolution rate standards exist, fibers with dissolution values inexcess of 100 ng/cm²-hr are considered indicative of a non-biopersistentfiber.

Table I shows fiber melt chemistries for various comparative andinventive fiber samples.

TABLE I SiO₂ MgO SrO Sample wt % wt % Al₂0₃ wt % CaO wt % Fe₂0₃ wt % wt% C1 55 0 45 0 0 0 C2 78 20 1.4 0.39 0.17 0 3 77.89 19.61 1.4 0.14 0.120.80 4 77.89 19.61 1.4 0.14 0.12 0.80 5 78.24 18.27 1.35 0.14 0.09 1.856 78.24 18.27 1.35 0.14 0.09 1.85 7 76.96 19.82 1.3 0.15 0.09 1.16 877.69 18.41 1.23 0.18 0.09 2.07 9 77.09 20.26 1.11 0.16 0.08 1.31 1075.41 20.65 1.06 0.17 0.09 2.68 11 79.8 15.70 1.01 0.21 0.14 2.6

Table II shows the results for shrinkage, compressive strength,compression recovery, and solubility for the fibers of Table I.

TABLE II Compress Compress Diameter Strength Compress Strength CompressMean Shrinkage 1260 C. Recovery Shrinkage 1400 C. Recovery μm 1260 C. %psi 1260 C. % 1400 C. psi 1400 C. % K ng/cm²hr C1 4.7 11.7 49.7 9.9 15.731.1 0 C2 8.5 8.2 15.8 9.2 3.2 3.7 260 3 4.1 4.5 10.8 43.6 4.7 9.5 27.61024 4 2.4 10.1 17.5 45.5 10.3 11.5 33.5 — 5 3.3 6 14.5 53.9 7.1 5.220.1 773 6 5.2 6.1 7.7 47.8 5.2 2.2 16.3 — 7 6.3 4.7 6.2 40.2 7 2.0 17.7924 8 7.8 3 5.4 37.3 4.1 0.9 4.4 596 9 4.15 4.4 9.9 46.8 4.5 4.5 14.41068 10 4.48 3.3 7.5 30.6 4.3 1.5 4.5 716 11 4.3 5.6 10.1 32.8 6.4 2.66.9 747

As shown in Table II above, magnesium-silicate fiber samples whichincluded a strontium oxide addition exhibited excellent linear shrinkagevalues. At 1260° C., magnesium-silicate fiber samples with a 0.8%strontium oxide addition exhibit improved shrinkage, and similarcompressive strength and compressive recovery properties as a refractoryceramic fiber (RCF). At 1400° C., the magnesium-silicate fibers with0.8% strontium oxide exhibit improved shrinkage and similar compressiverecovery as an RCF. The shrinkage results for inventive example 4 ofTable II are considered to be within experimental error. However, theRCF fails to dissolve in physiological fluid. In contrast, themagnesium-silicate fiber sample dissolved in simulated lung fluid at arate of 1024 ng/cm²hr.

Also shown in Table II, magnesium-silicate fiber samples with astrontium oxide addition compare favorably to ISOFRAX® fibers. At 1260°C., magnesium-silicate fiber samples with a 0.8% strontium oxideaddition exhibit improved shrinkage, improved compressive strength, andimproved compressive recovery properties as ISOFRAX® fibers. At 1400°C., the magnesium-silicate fibers with 0.8% strontium oxide exhibitimproved shrinkage, improved compressive strength, and improvedcompressive recovery properties as ISOFRAX® fibers. Further, themagnesium-silicate fibers with 0.8% strontium oxide additions werenearly four times more soluble (1024 ng/cm²hr vs. 260 ng/cm²hr) as theISOFRAX® fibers.

Also shown in Table II are the results for the testing ofmagnesium-silicate fiber samples with 1.9% strontium oxide additions. At1260° C., magnesium-silicate fiber samples with a 1.9% strontium oxideaddition exhibit improved shrinkage, similar compressive strength, andimproved compressive recovery (53.9% vs. 49.7%) properties as arefractory ceramic fiber (RCF). At 1400° C., the magnesium-silicatefibers with 1.9% strontium oxide exhibit improved shrinkage and similarcompressive recovery properties as an RCF. The RCF fails to dissolve insimulated lung fluid, but the magnesium-silicate fibers exhibit asolubility of 773 ng/cm²hr in simulated lung fluid.

Also shown in Table II are the results for testing magnesium-silicatefiber samples with a 1.9% strontium oxide addition as compared toISOFRAX® fibers. At 1260° C., magnesium-silicate fiber samples with a1.9% strontium oxide addition exhibit improved shrinkage, improvedcompressive strength, and improved compressive recovery properties asISOFRAX® fibers. At 1400° C., the magnesium-silicate fibers with 1.9%strontium oxide exhibit improved shrinkage, improved compressivestrength, and improved compressive recovery properties as ISOFRAX®fibers. Further, the magnesium-silicate fibers with 1.9% strontium oxideadditions were nearly three times more soluble (773 ng/cm²hr vs. 260ng/cm²hr) as the ISOFRAX® fibers.

The magnesium-silicate fibers with strontium oxide additions exhibitlower shrinkage than current commercial fibers following exposure totemperatures up to 1400° C. The magnesium-silicate fibers with strontiumoxide additions also retain equivalent, or superior mechanicalproperties following exposure to temperatures up to 1400° C. whencompared to existing commercial fibers.

The present fiber composition exhibits lower shrinkage compared tostandard RCF and higher fired strength measured by overall resiliencyfollowing compression after exposures to temperatures of 1260° C. and1400° C. The improved inorganic fiber composition may exhibit superiorperformance to higher temperatures, possibly up to 1500° C.

While the inorganic fiber, thermal insulation, methods of preparing theinorganic fiber, and method of insulating articles using the thermalinsulation have been described in connection with various embodiments,it is to be understood that other similar embodiments may be used ormodifications and additions may be made to the described embodiments forperforming the same function. Furthermore, the various illustrativeembodiments may be combined to produce the desired results. Therefore,the inorganic fiber, thermal insulation, methods of preparing theinorganic fiber, and method of insulating articles using the thermalinsulation should not be limited to any single embodiment, but ratherconstrued in breadth and scope in accordance with the recitation of theappended claims. It will be understood that the embodiments describedherein are merely exemplary, and that one skilled in the art may makevariations and modifications without departing from the spirit and scopeof the invention. All such variations and modifications are intended tobe included within the scope of the invention as described hereinabove.Further, all embodiments disclosed are not necessarily in thealternative, as various embodiments of the invention may be combined toprovide the desired result.

The invention claimed is:
 1. An inorganic fiber comprising afiberization product of about 65 to less than 70 weight percent silica,about 14 to about 34 weight percent magnesia, and about 1 to about 5weight percent strontium oxide.
 2. The inorganic fiber of claim 1,wherein said inorganic fiber comprises the fiberization product of about65 to less than 70 weight percent silica, about 14 to about 34 weightpercent magnesia, and about 2 to about 5 weight percent strontium oxide.3. The inorganic fiber of claim 1, wherein said inorganic fibercomprises the fiberization product of about 65 to less than 70 weightpercent silica, about 14 to about 34 weight percent magnesia, and about3 to about 5 weight percent strontium oxide.
 4. The inorganic fiber ofclaim 1, wherein said inorganic fiber comprises the fiberization productof about 65 to less than 70 weight percent silica, about 14 to about 34weight percent magnesia, and about 4 to about 5 weight percent strontiumoxide.
 5. The inorganic fiber of claim 1, wherein said inorganic fibercomprises the fiberization product of about 65 to less than 70 weightpercent silica, about 16 to about 25 weight percent magnesia, and about1 to about 4 weight percent strontium oxide.
 6. The inorganic fiber ofclaim 1, wherein said inorganic fiber comprises the fiberization productof about 65 to less than 70 weight percent silica, about 16 to about 25weight percent magnesia, and about 1 to about 3 weight percent strontiumoxide.
 7. The inorganic fiber of claim 1, wherein said inorganic fibercomprises the fiberization product of about 65 to less than 70 weightpercent silica, about 16 to about 25 weight percent magnesia, and about1 to about 2 weight percent strontium oxide.
 8. The inorganic fiber ofclaim 1, wherein said inorganic fiber comprises the fiberization productof about 65 to less than 70 weight percent silica, about 16 to about 25weight percent magnesia, and about 1 to about 1 weight percent strontiumoxide.
 9. The inorganic fiber of claim 1, wherein said inorganic fibercomprises the fiberization product of about 65 to less than 70 weightpercent silica, about 17 to about 21 weight percent magnesia, and about1 to about 4 weight percent strontium oxide.
 10. The inorganic fiber ofclaim 1, wherein said inorganic fiber comprises the fiberization productof about 65 to less than 70 weight percent silica, about 17 to about 21weight percent magnesia, and about 1 to about 3 weight percent strontiumoxide.
 11. The inorganic fiber of claim 1, wherein said inorganic fibercomprises the fiberization product of about 65 to less than 70 weightpercent silica, about 17 to about 21 weight percent magnesia, and about1 to about 2 weight percent strontium oxide.
 12. The inorganic fiber ofclaim 1, wherein said inorganic fiber comprises the fiberization productof about 65 to less than 70 weight percent silica, about 17 to about 21weight percent magnesia, and about 1 to about 1 weight percent strontiumoxide.
 13. The inorganic fiber of claim 1, wherein said inorganic fibercomprises greater than 0 to about 11 weight percent zirconia.
 14. Theinorganic fiber of claim 1, wherein said inorganic fiber comprises 1weight percent or less iron oxide, measured as Fe₂O₃.
 15. The inorganicfiber of claim 1, wherein said inorganic fiber comprises substantiallyno alkali metal oxide.
 16. The inorganic fiber of claim 1, wherein saidinorganic fiber has an average diameter of greater than 2 microns. 17.The inorganic fiber of claim 1, wherein said inorganic fiber exhibits ashrinkage of about 10% or less at 1260° C. for 24 hours.
 18. Theinorganic fiber of claim 1, wherein said inorganic fiber exhibits ashrinkage of about 5% or less at 1260° C. for 24 hours.
 19. Theinorganic fiber of claim 1, wherein said inorganic fiber exhibits ashrinkage of about 10% or less at 1400° C. for 24 hours.
 20. Theinorganic fiber of claim 1, wherein said inorganic fiber exhibits ashrinkage of about 5% or less at 1400° C. for 24 hours.
 21. A method ofinsulating an article at 1400° C. or greater, including disposing on,in, near or around the article, a thermal insulation material, saidinsulation material comprising a plurality of inorganic fiberscomprising the fiberization product of claim
 1. 22. An inorganic fibercontaining article comprising at least one of bulk fiber, blankets,blocks, boards, caulking compositions, cement compositions, coatings,felts, mats, moldable compositions, modules, papers, pumpablecompositions, putty compositions, sheets, tamping mixtures, vacuum castshapes, vacuum cast forms, or woven textiles, braids, cloths, fabrics,ropes, tapes, sleeving, wicking, said inorganic fiber containing articlecomprises a plurality of inorganic fibers comprising the fiberizationproduct of claim 1.